1. Field of the Invention
The present invention relates to the field of LED light-adjustment techniques, and in particular to an LED light-adjustment driver module, backlight module and liquid crystal display device.
2. The Related Arts
Due to the advantages of low energy-consumption, environmental friendliness and high efficiency, the LED backlight is widely adopted in many applications.
Because the luminance of the backlight must be adjusted, light-adjustment must be performed on LED. At present, the majority of the light-adjustment uses pulse width modulation (PWM) technique. Referring to FIG. 1, FIG. 1 is a schematic view showing the structure of a known LED light-adjustment driver circuit. The LED light-adjustment driver circuit comprises a comparator A, a current source S and a capacitor C; one end of capacitor C being connected a first input end of the comparator A, and the other end being grounded. The current source S is connected to the first input end of the comparator A. A second input end of the comparator A inputs a threshold voltage V. The LED light-adjustment driver circuit will respond to PWM signal P. When PWM signal P is high, current source S outputs a current to charge capacitor C. When the voltage of capacitor C rises to exceed the threshold voltage V, the comparator A outputs high for adjusting the luminance of the LED backlight.
However, when the known LED light-adjustment driver circuit adjusts the luminance of the LED backlight, a flickering problem exists. In the condition that the duty cycle of the PWM signal P is small, when the LED backlight is lit for the second time, because a voltage exists on the capacitor C, the voltage is backlight, but will only last for a short time. Then, the current source S charges the capacitor C. Because the duty cycle of the PWM signal P is small, the charge time for the capacitor C is short. Therefore, the voltage on capacitor C will not reach the threshold voltage V. Only after the PWM signal P goes through a plurality of high levels, the voltage on capacitor C can exceed the threshold voltage V, and the comparator A can output high level to light LED backlight. During lighting the LED backlight, because the voltage on capacitor C takes longer time to reach the threshold voltage V, a flickering problem occurs, which affects the lighting quality.